(CNN) President Trump says he's sending the military to help guard the border until his long-promised wall is built.
Key details about the President's plans to deploy National Guard troops have yet to be announced -- including how many troops he's requesting, where they'll go, how long they'll be there, exactly what they'll do and how much it will cost.
But the idea of deploying the National Guard to help enforcement along the border is nothing new.
President George W. Bush and President Barack Obama both did it, in two operations that cost a total of more than $1.3 billion.
Critics called those deployments costly and inefficient. Supporters said they helped US Customs and Border Protection fill in gaps and step up enforcement.
Here's a snapshot of what happened during those operations, according to reports from the Government Accountability Office and congressional testimony:
Name: Operation Jump Start
When it happened: June 2006-July 2008
Cost: $1.2 billion
Who was deployed: 6,000 National Guard troops deployed to California, Arizona, New Mexico and Texas.
Assists with undocumented immigrant apprehensions: 186,814 (11.7% of the total apprehensions on the Southwest land border in that period)
Assists with drug seizures: 316,364 pounds of marijuana (9.4% of all marijuana seized on the Southwest border in that period)
Name: Operation Phalanx
When it happened: Initially from July 2010-June 30, 2011, then extended
Cost: $110 million for the first year
Who was deployed: Initially 1,200 National Guard troops. In 2012, the number of troops was scaled back as the focus shifted from boots on the ground to aerial surveillance.
Assists with undocumented immigrant apprehensions: 17,887 in the first 11 months (5.9% of the total apprehensions on the Southwest land border in that period)
Assists with drug seizures: 56,342 pounds of marijuana in the first 11 months (2.6% of all marijuana seized on the Southwest border in that period)